Telephone-exchange system



July 1, 1925.

E. F. TRAPP Filed May 19, 1924 TELEPHONE EXCHANGE SYSTEM 13 Sheets-Sheet 1 July 7, 1925. 1,544,958

E. F. TRAPP TELEPHON E EXCHANGE SYSTEM Filed May 19 4 July 7, 1925. 1,544,958

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July 7, 1925.

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E. F. TRAPP TELEPHONE EXCHANGE SYSTEM Filed May l9, 1924 13 Sheets-Sheet 7 E. F. TRAPP TELEPHONE EXCHANGE SYSTEM July 7,1925. I 1,544,958

Filed May 19. '1924 l3 slheets-sheet 8 I l l I I I L 5 l E L July 25,1925

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E. F. TRAPP TELEPHONE EXCHANGE SYSTEM Filed May 19, 1924 13 Sheets-Sheet l1 Mme/flow; I [mm 5 Try/p July 7, 1925. 1,544,958

' E. F. TRAPP TELEPHONE EXCHANGE SYSTEM Fil May 19, 924 13 Sheets-$heet l2 July 7, 1925.

E. F. TRAPP TELEPHONE EXCHANGE s YsTEM 13 Sheets-Sheet 1:5

' Filed May 19, 1924 Patented July 7, 1925.

UNITED STATES PATENTAVOFFICE.

EDWIN F.

TRAPP, 0F VALLEY STREAM, NEW YORK, ASSIGNOB, T0 WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed May 19, 1924. Serial No. 714,234.-

To all whom it may concern. 1

Be it known that I, EDWIN F. Turn, a citizen of the United States of America, residing at Valley Stream, Long Island, in the county of Nassau and State of New York, have invented certain new and useful Improvements in Telephone-Exchange Sys tems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to a testing system for use in machine switching offices for testing selector and connector units.

An object of this invention is to provide an improved testing system. I

Switching units of an automatically operated telephone exchange are made up of control apparatus, relays and auxiliary circuits to control their automatic progression and to further control other switching units and the lines to which connections are established. A large number of such switching units are required in a system of this kind, any one of which may be arbitrarily selected when idle to complete a service connection. Thus, it is apparent that a switching unit giving inefficient service is not immediately noticed. Since the apparatus of a switching unit requires adjustment within limited variations, it is important that these units be regularly tested to determine their ability to render efficient service. In order to reduce the cost of such maintenance, it

is desirable to use a testing system requiring a limited amount of manual operation, confining the latter for the most part of the operation of keys and the observation of lamp signals.

\Vhile the invention about to be disclosed may with slight variations be applied to test any type of selector and connector switches. it has been particularly arranged for testing district selector and line finder circuits of the type disclosed in the application of Frank S. Irvine, Serial No, 602,948, filed Nov. 24, 1922 and in-the following patcuts to Frank S. Irvine: 1,461,528, issued July 10, 1923; 1,505,710, issued Aug. 19, 1924 and 1,507,966, issued Sept. 9, 1924.

A feature of this invention resides in the use of a common testing device for particularly testing the operation of selector switches of the above mentioned type.

A further feature of this invention relates to the provision of means for operating selector switches of the above mentioned type in simulation of the manner in which such switches function. under actual service conditions and for. observing through the medium of supervisory apparatus the accuracy with which these switches function.

A further feature resides in-the manner of establishing a connection between the testing device and the selector to be tested.

A further feature relates to a method of determining whether the line finder selector is in contact with the desired line.

A further feature may be found in the test of the message register charging'circuit.

A further feature is the test of collect and return circuit.

A further feature resides in the method of repeating any one of the three parts of a routine test on the same selector any numthe, coin 'ber of times.

A further feature is, an arrangement whereby when two test circuits of the type herein disclosed are employed in the same oflice, the one first seizing a district forltest may block the second until the first has caused the district to select its associated terminals. i

Further features may be found in the method of determining the type of selector circuit to be tested, the apparatus for 'advancing from one circuit to another, and the means for sending a series of impulses through the testvcircuit in the sender which has been associated with a districtto cause the district to select a set of terminals associated with the test circuit.

The apparatus to be tested consists of a line finder district circuit, shown in Figs. 3 and 4, which is associated by means of proper conductors to line finder connectors of the type shown in Fig. 10. Each twenty district and line finder circuits have associated of the type indicated at 710 and 1020.

Fig. 2 is permanently associated with the test circuit and the line finder selector is caused to select this circuit. While it will be shown that this test circuit may be used totestdistrict selector and line finder circuits of the coin collect, flat rate or the message rate one and two party type, for the sake of simplicity of disclosure, only the two party message rate circuit has been shown. For the coin collect type district circuit reference may be had to Fig. 2 of the patent of E. Mills, No. 1,504,261, issued Aug. 12, 19-242, and for flat rate and message register single party type reference may be had to the a plication of F. Irvine, Serial No. 602,948, also above noted.

Reference may now be had to the accompanyin drawings:

Fig. 1 shows a start circuit of the type herein referred to having a regular and an emergency circuit. There is also associated with the two circuit-s an auxiliary test circuit for testing the line finder selector. Its function will become more apparent after the description of eperation has been given.

Fig. '2 shows the relays and apparatus which are ordinarily associated with a subscribers line.

Fig. 3 shows a panel line finder selector switch, a party selector stepping switch and the necessary control relays.

' Fig. 4 shows a district panel type selector switch, its associated repeating coil, relays and sequence switches in addition to a sender selector and a representation of a sender. Since this sender circuit is not a part of the invention and since it is fully disclosed in Patent No. 1,395,977 issued November 1, 1921 to F A. Stearn and F. J. Scudder, ithas been represented here by the rectangle 430;

' Figs, 5 to 13, inclusive, show the arrangement of the test circuit itself.

Fig. 5 contains a. duplication of the district selector frame terminals shown on Fig.

4, the connecting conductors being left out' for the sake of clearness. A second test cir cuit, which is similar in all respects to that shown on Figs. 5 to 13, inclusive, is repre sented diagrammatically by the rectangle 500 in Fig. 5. Auxiliary relays, interrupters and resistance elements together with signaling lamps are also shown.

Fig. 6 contains additional lamps, relays and conductors'and also a key which, when operated, causes the test circuit to repeat a complete cycle of routine tests.

Figs. 7 and 10, when taken together, show the means for selecting the circuits for test. The system used is a pyramid system. Selector switches 700 and 1000 are the master switches. These switches have associated with their terminals, twenty group switches In Fig. 7 the terminals of each group switch are connected to astart circuit as shown in Fig. 1, conductors 717 to 721, inclusive, on Fig. 7 being connected to conductors 717 to 721, inclusive, on Fig. 2. In addition to the master and group switches, there are also line finder switches shown in Fig. 10 which are connected by means of their, terminals and conductors 10 19 to 1051, inclusive, through Fig. 2 to the line finder circuit of Fig. 3. While only one master, one group and two line finder selector switches have been shown, it should be understood that any number of these switches may be employed with slight modification or" the drawings without departing from the spirit of the invention. The number of switches provided depends upon the number of district and line finder circuits to be tested. Each line finder switch has access to twenty line finder and district circuits, each group switch has access to twenty line finder selectors and each master switch controls twenty group switches. Therefore, when one master switch is employed, access may be had to twenty times twenty or four hundred district and line finder circuits. It is the usual custom to employ two master switches in each oificc so that a total of eight hundred circuits may be subject to routine test.

Fig. 8 shows the test circuit, its controlling sequence switch and associated cams a dial and key for selecting a particular circuit to be tested, and within the cash-dot rectangle, a pulsing sequence switch is provided with two cont-rolling relays. The cuttings of the cams of this sequence switch differ from the standard sequence switch in that they are cut in twenty positions. Besides, the cuttings of cam 854, which are written within circles, are special cuttings arranged to be closed 2 degrees before to 2 degrees after the positions indicated.

Fig. 9 shows a sequence switch known as a class sequence switch which takes settings determined by the particular type of the district circuit which is under test. A number of lamps are shown which light as a visual indication of the type of circuit under test. A key is also shown which controls the lighting or these lamps. another key 920 is provided for making a false charge test which will be more fully explained hereinafter.

Fig. 11 discloses a number of keys which are essential to the operation of the circuit, a. start key 1 for controlling the start of a routine test, control advance key 2 for advancing the test circuit when it halt-s due to the development of trouble, and a pass busy key 4 for enabling the line finder switch to pass over the terminals of a busy line finder district circuit and proceed to test the next selector. Keys 3, 7 and 8, respectively, are used to repeat the series of tests made in the first, second and third revolutions of the test to record the number of times a busy terminalhas been passed over, a single test-register which records the number of single tests made, and a lamp signal indicating that the circuit under testis busy.

Fig. 12 contains a complete test register for indicating the number ofcoiiiplete tests which have been made and an arrangement of relays and lamps rtor indicating when more. .than one group selector has been stepped oft normal.

In Fig. 18 is shown a class stepping switch whichoperates in synchronism with the line finder connector switch and by an arrangement of lamps indicates at any time the number oi": the district circuit under test.

A group of relays is also disclosed herewhich are employed for controllingthe setting 01 class sequence switch 900 ofFig. 9. Within the dot-dash rectangle is shown a time alarm circuit which is. similar in all respects to that disclosed in the applicationof Arnold S. Bertels and Edwin F. Trapp, Serial No.

679,812 filed. December .8, 1923. Atthe-extreme. rightof this figure is indicated a series of lamps which light in order as an indication ofthe' number of the line finder connector which is at each moment employed. Only two of these lamps have been shown connected, the first and the twentieth, since only the first and the twentieth line finder connectors have been disclosed ,on Fig. 10. But it'should-be understood that eaclrof the other lamps is ,connectedto a line finder connector.

General description.

The operation of the start .key, shown'in Fig. 11, at the beginning of a routine test causes the time measure switch of Fig. 13 to begin to measure time. Theoperation of this key. also causes the master selector switch tostep to its first terminal. The test circuit is then connected tothe first group switch, which, in turn, is caused to step to" its first terminal, in turn, causing the first line finder connector switch to r,otate to its first terminal.

A condition is placed uponthe first terminal of the line finder connectors. in order, to test the type of circuit. 1 All of the line finder and district selector circuits associated with any one line finder connector switch are of the same type, being either oneor two party messagerate, coin collect or 'fiat ratecircuits. .With the line finder connector switch on terminal; 1 a test'is madeto determine, which type is associated with the switch. Upon this determination the classrelaysof Fig. 13 and. the class sequence switch of Fig. 9 are set in the proper position to direct the test circuit in its selection of the kind of tests to be made. It should be understood that different tests are made on the difi'erent types of circuits.

Upon the completion of the class switch setting, the line find-er connector steps to its next terminal, thus connecting the test circuitto the first line finder and district circuit to be tested. Since it is possible that this circuit may not be in condition for test,

certain preliminary tests must be made. These consist of a test for a spare terminal and for a busyor idle circuit. If the terminal 'upon' which the line finder connector is standing is spare, that is, it is not connected to any circuit the connector is caused automatically to pass over this terminal to the next; terminal. It the circuit is found to be busy either in regular traffic or because it has been artificially made busy, the connector switch will remain upon the terminal and wait for it to become idle. A lamp signal is lighted as an indication that the terminal is busy and, if it is so desired,

the operator may cause this terminal to be passed over. It the .circuit to be tested is found in an idle condition the line finder is caused to perform the same functions necessary for the completion of an ordinary call. The test line is hunted for and tests are made to determine whether or not the line finder elevator moves upwardly and also whether or not it comes to rest on the proper line; The district circuit is then caused to advance'to its second position to select an idle sender. Upon the selection of the sender a dialing path is completed through the district to the test circuit. The pulsing sequence switch of Fig. 8 then proceeds to transmit a series of impulses in simulation of the code transmitted by the calling dial.

This code isregistered on the registers of the sender and the district is advanced, making brush and group selections and hunting for the trunk leadingto the test circuit.

The code transmitted to the sender is such that it would cause the district circuit to rest in a position in which its repeating coilis shuntedout of the talking circuit;

Various special operate, non-operate and release conditions'are placed in the circuit of both of the district supervisory relays and the behavior under these conditions is reported in the test circuit. Upon com pletion of the relay tests, the districtis released, permitting its return to normal. The

test circuit sequence switch is then caused to make a. second revolution. Another code is transmitted, this second being such that the district selector is caused to stop in a position inwhich the repeating coil is included in the talkingcircuit. Tests similar to those made during the first revolution of the test se uence switch are again made on the dis trict supervisory relays and the district eircuit is advanced into its message register charging position where it is tested for the registration of a call made by the first party of a two-party line. The registration of a call made by the second party of the twoparty line is tested on the third revolution of the test circuit sequence switch. During this revolution the same code is transmitted as was transmitted during the second revolution, the district circuit assuming the same position.

Upon the completion of these tests the line finder connector is st pped to Iiext terminal and the next line finder and district selector is tested in the same manner as the first. hen all of the line finder and district circuits associated with the line finder connector are tested, the group swit h is advanced to its next terminal and the test is conducted on the circuits associated with the next line finder connector. When the group switch has made a complete revolution the master switch advances to its next terminal, permitting the circuits associated With the next group switch to be tested. If a second Inaster switch is provided, the circuits associated therewith are tested upon the completion of the tests of those connected to the first master switch.

Initiation 0 f test.

It is thought that the invention wilLbe more apparent from a detailed description of theoperation of a routine test. An operator desiring to make a complete test upon all the district selector circuits and line finder circuits to which this test circuit has access, depresses a start key 1. Upon the operation of this key, a circuit is closed from grounded battery, winding of the power magnet of sequence switch 800, lower right contact of cain 801, conductor 802, left back contact of relay 1201, outermost right back contact of relay 1202, conductor 1203, operated contact of key 1 to ground at the normal cont-act of key 2. The power magnet of sequence switch 800 is energized in this circuit, moving this sequence switch from position 1 to position 2. A circuit is also completed from grounded battery, winding of start relay 1204, conductor 1205 to ground at the operated contact of key 1. Relay 1204a energizes in this circuit, The operation of the start ke 1 also causes the time alarm circuit shown in Fig. 13 to func tion b completing a circuit for the energiz'ation of relay 1301. Thiscircuit may be tracedfrom grounded batter winding of relay 1301, brush arm 1302 and its associated normal contact, conductor 1303 to ground at the operated conta t of start key 1. The functioning of this time alarm circuit will be more fully explained hereinafter.

With sequence switch 800 in position 2, a circuit may be traced from ground, right back contact of relay 803, conductor 804, left normal Contact of relay 1, outer left normal contact of relay 602, left normal contact of relay 603, conductor 604, lower right contact of cam 805, upper left contact of cam 806, conductor 807, left Winding of relay 605, conductor 606, brush mm 701 of the first master selector switch 700 and its associated normal terminal, conductor 707, right back contact of relay 607, conductor 60S, brush arm 1001 ofthe second master selector- SWitCl i 1000 and its ESSGCiMet-l 110imal terminal through the winding of relay 1007 to rounded battery. Relays 605 and 1007 are energized in this circuit The energizatien of relay 1007 provides operating path for the stepping magnets or master switches 700 and 1000. The circuit for master switch 700 may be traced from grounded batter winding of magnet 700, armatnne and back contact of the magnet, right operated contact of relay 1007, conductor 1008, right contacts of cam S, conductor 809, armature and back contact of relay 609,- inner ri ht armature and back contact of relay 010, conductorell, normal contacts of keys 6, 3, 7, 8 and 2, cond-nctbr12, back contact of relay 1201, conductor 1206, intermediate back-contacts" of relays 1304a'nd 1305, next to the inner back contacts of relays 1306 and 1307, conductor 1308, upper left and lower right contacts of cam 810 130 ground, The energization of relay 605 completes a short circuit aroundthe winding of rela 612-. This short circuit may be traced from one side f the winding of relay 612, front contact of relay 605, coiiductor 613, lower right contact of earn 808, conductor 1008, right front contact of relay 1007, armature and back contact of stepping magnets 700 and 1000 in parallel, inner left front contact of relay 1007, conductor 1009, lower right and upper left contacts of cam-811, conductor 812 back to the other side of the winding of relay 612.

Advance of master selector.

This short circuit is broken upon-the operation of the master step-ping magnets 700 and 1000 and relay 612 then becomes ener= gized. A circuit may then be traced from grounded battery, winding of the power magnet of sequence switch 800, lower left contact of cam 801, conductor 813, outer right back contact of relay 1207, conductor 1208, front contact of relay 612, back contact of relay 614C, conductor 615, normal contacts of key 6, conductor 13, right back contact of relay 1209, conductor 1210 to ground at the upper left contact of earn 901. Sequence'sWitch 800 is then advanced out of position 2 .into position 3. As this sequence switch leaves position 2, relays6'05,

; p to ground I at the upper lett an'd'lower right; contacts of cam 810. Magnets? 10 and 1020 for relay 612 and 1007 and magnets 700 and1000 deenergize. The release of the" two latter magnets causes the brush assemblies of their associated switches to step to their first normal terminals. It will be noted that the energization of relay 1007 completed an obviouscircuit forrclay 1010. Relay 1010 closes a circuit from grounded battery through its left armature and front con tact, lamp 1011, conductor 1012 to ground at the "operated contact 01" key 902. This key may be operated at the beginning of a te-st when lamp signals are desired). Lamp 1011 lights as an indication that the master switch has been stepped off normal.

I Advance of; group selector.

As soon as the master switch reachesitsfirst terminal, a holding circuit is completed 1010 from grounded battery, winding of relay 1010, brush arm 1006 and its associated first off winding of relay 1013 to ground. The com pletion of this circuit causes the energiza tion ofrelay 1013, which in turn compl ete's a circuit from grounded battery, resistance" 1015, inner left front, contact of relay 1013,

conductor 10141, intermediate right back contact of relay 1202, winding ot'relay 1211,

conductor 1212 to ground at the normal con-' grounded battery', winding of relay 1018,

brush arms 1021 and 711 and their associated normal terminals, brush arm 1002 and its associated first terminal, conductor-708, right winding of relay 605, conductor 616, upper right contacts of cams 806rand 805 conductor 81 1, inner left back contact of relay 602, left back contact of relay 601, conductor 804' to ground at the right back contact of relay 803. "Relays1018 and 605 'are energized in this circuit; Relay 1018, upon operating, completes a circuit from grounded battery, through the, windings, armatures and back contacts of stepping magnets 1020 and 710 in parallel, outer front'contact of relay 1018, conductor 1008, right contacts of cam 808, conductor 809, normal contacts of relay 609, inner right back contact of relay' 610, conductor 611,normal contacts of. keys 6,.

3, 7 8 and 2 in series, conductor '12 outer right back contact of relay 1201, conductor 1206, intermediate back contacts of relays. 1304C .and 1305, next to the inner back con-' tacts of relay 1306 an'd'1307', conductor 1308 normal terminal, leftand 501 energize in this circuit.

are energized in this circuit. "The energize tion of relay 1018 closes a short circuiting path around the winding of relay 612. This circuit may be traced from one side of the winding of relay 612, conductor 812, upper left and "lower right contacts of earn 811,

conductor 1009, front contact of relay'1018, back contact of stepping magnet 1020, outer front contact of relay 1018, conductor 1008, lower right contact of cam 808, conductor 613, front contact of relay 605 to the other side of the winding of relay 612. When magnets 710 and 1020 attract their armatures this short circuit is opened and relay 612 is energized, completing a circuit from grounded battery, winding of the power magnetof sequence switch 800, lower left contact of cam 801, conductor 813, outer right back contact of relay 1207, conductor 120 8, front contact of relay 612, back contact of key 6, conductor 13, right back contact of relay 1209, conductor 1210 to ground at the upper contact of cam 901. Sequence switch 800 is advanced from position 3 into position 4 over this circuit.

v 7 Selection of line finder. As sequence switch 800 leaves position 3,

relays 612, 605 and 1018 and steppingmagnets 710 and 1020 deenergize. The deenergization of the stepping magnets causes the brush assemblies of the associated selector switches to step to the first terminal. A circult may now be traced from grounded battery, winding of relay 1027, brusharm 1026 and its associated first terminal, winding of relay 1019, right windingofrelay 1013 "to 1019 and 1013 ene-r gizein this circuit. When relay 1019' at?" tracts its armatures, a circuit is closed from ground through the inner front contact of: relay 1019, conductor 1037 through the wind grounded battery, enerr ground. Relays 1027 ingot relay 603 to gizing this-relay. A circuit may also be traced, from grounded battery throughthe winding ofrelay 1029,'brush arm 1022 and relay 614, conductor 615, normal contacts of its'assoc-iated first terminal, conductor 1038,

right winding of relay 501, lower right contact of cam 806, conductor 81a, inner left back contact of relay 602, left backcontact of relay 601, conductor 804C to ground at the right back contact of relay 803. Relays 1029 gization of relay 1029 completes a circuit from grounded battery, winding of stepping magnet 1030, armature and back contact of the magnet," outer front contact; of'relay 1029, conductor 808, conductor 809, back contactfof relay 609, innerrightbackcontact of relay 610, conductor 611 through the normal contacts of keys 6, 3, 7, 8 and 2 in series, conductor 12, outer right back contact of relay 1201,

conductor 1206, intermediate'armatures and The ener- 1008, right contacts of cam;

backont ts of el ys ,3 4 nd 0 ,.next

totl e inner back contacts of relays 1306 and 1307, conductor 1308, upper left and lower right contacts of cam 810 to ground. The line finder selector magnet 1030 becomes energized and the short circuiting path for relay 612, which, as can obviously be seen, was transferred through the back contact of stepping magnet 1030, is now broken and this relay operates. Sequence switch 800 is now advanced from position 4 into position 5 over a circuit which may be traced from grounded battery through the winding of the power magnet of this sequence switch, lower left contact of cam 801, conductor 813,, outer right back contact of relay 12.07,. conductor 1208, front contact of relay 612, back contact of relay 614;, conductor 615, normal contact of key 6, conductor 13, right back contact of relay 12 09, conductor 1210 to ground at the upper contact of cam. 901.

The .energization of relay 1027. completes circuit from grounded battery through its right. front contact through lamp 1326 over conductor 1012 to ground at the contact of lamp key 902. Lamp 1326 is lighted as an indication that the first line finder connector has been associated with the group switch and is now offnormal. As sequence switch .800 leaves position/l, relays 612, 501 and 1029 and stepping magnet 1030 deenere gize, the release of. the latter magnet causing its brush assembly to step-to its first terminal.

Positioning of class circuit.

In position 5 of sequence switch 800 a circuit is in existance from grounded battery, through the winding of relay 13.15, conductor 1327, upper contacts of cam 815, con, ductor 816, brush arm 1313 and its normal terminal, conductor 1328, outermost right back contact of relay 1213, conductor 121 1 tov ground through the lower contact of cam 903 Relay 1315. operates in preparation for setting the proper class relays, These relays, designated 130 i, 1305, 1306,1307 and 13,16, are operated either singly or in groups in series with, relay 1317 as determined by the particular class of district circuit to which the connector switch associated with magnets 1.030 and 1040. (and other magnets not shown) are connected. The various types of district selector and line finder circuits to which this test circuit has access,

are message register, one and two party, coiircollect and flat rate, but for simplicity of. disclosure only the message-rate, two party district Selector-and line finder circuit ve b en shown.- T ppl ati of hi test circuitv to the other types of district selector and line finder circuits will become obvious after the following description. has been made. I

.AS LlmiHgW them, that two party district conductor 1335, to

selec o a gd line nder O Q -lits are nne t: ed. to the termrnals of the. connector bank controlled by magnet 1030, it will be seen,

that the energization of class relay 1315 will complete a circuit for energizing relays 13 07 and1317. Thiscircuit may be traced from grounded battery, brush arm 1311 and its associated normal terminal, windings of relays 1317 and 1307 in series, innermost front contact of relay 1315, conductor 1331, brush arms 1034, 102 l and 100 i and their associated first terminals, conductor 104%7, upperright contact of cam 815 to ground over the circuit previously described for the operation of relay 1315. Relays 1307 and 1317 are energized. Relay 1317, by opening its back contact, prevents the premature return to normal of theclass selector swi-tOh controlled by magnet 1310. Relay 1307, upon energizing, completes a locking circuit for itself through its innermost front contact,

conductors 1329 and 1215 to ground at. the

normal contact of key 5. Upon the energization of relay 1307,.seqnencc switch 900 is advanced into position 2,, which is the first positionv assumed by the sequence switch in preparation for testing two party, message rate district and line finder c rcuits, The circuit for advancing thls sequence switch may be traced from grounded battery,wincl- I ing of. the power magnet of sequence switch 900, lower left contact of cam 9Diw0nd-uctor 05;, ou e mos ro con act of relay 1 outermost backcontact of relays 130.6, 1.305 and 1304, conductors 1330 and 557, upper left contacts. of cam 817, conductor 818, to ground at the outer right back contact of relay 1216. As. soon as the circuit for sequence switch 900 is completed, a parallel circuit is also completed for relay 1207 over conductor 1217. This relay remains operated during the advance of sequence switch 900 to prevent the premature advance of sequence switch 800 out of position 5 by opening the advance circuit for the sequence switch at its outer left armature and back contact.

' If districts of the'coin collect type are cor nected to the line finder connector, then con ductor 1335 instead of 1.331 is connected to the first terminals of the brush arms 1034.. .L. d 104A and. relays 1.3.06 and 1317 arev energized in a circuit which may be traced. from grounded battery, brush arm 1 11 and its associated normal terminal, windings of relays 13:17 and .1306 in series, next to the: inner front: contact of relay 1315i, ground as previously described on brush. arm 1034 Relay 1317, upon operating, performs the same function arcs served by V as, above described. Relay 1306 lockstl rou gh itsv innermost front contact. to: ground on; conductor 1329. Sequence switch 900 isthen advanced to position 5 which is the first posis tioa for testi g. districts of the oin collect loo ' type.

switch 900 extends from battery through the The circuit for advancing sequence winding of sequence switch power magnet 900, upper left contact of cam 904, conductor 955, outermost front contactof rel'ay 1306, outermost back contacts of relays 1305 and 1304, conductors 1330 and 557 upper left' contact of cam 817, conductors 818' and'30 to ground atthe outer left back contact of relay 14. t

For districts of the flat rate type conductor 1336 is connected to brush arms 1034 and 1044 and relays 1305 and 1317 are operated, the circuit for these relays. extending through'their'windings'in series, next to the outermost front contact of relay 1315, conductor 1336, to ground as previously described on brush arm 1034. Sequence switch 900 is then advanced to position 8 in a circuit which may be traced from battery through the winding of magnet 900, upper right contact of cam 904, conductor 944,

outermost front contact ofrelay 1305, outermost back contact of relay 1304 to ground as traced on conductor 1330. Conductor 1337 is connected to brush arm 1034 as an indication that message rate single-party circuits are associated with the connector and relays 1304 and 1317 are energized in a circuit extending through the'outermost front contact of relay 1315. Sequence switch 900 advances to position 2 over conductor 905 as described for districts of the message rate two-party type. When sequence switch900 comes to rest in position 2, relay 1207 'dee'nergizes. It

should be noted that as sequence 800 entered position 5, relays 1029 and 501 were energized in a circuit which may be'traced from grounded battery, winding of relay 1029,

brush arm 1022 and its associated first terminal, conductor 1038 right winding of' relay upper right contact of cam 805, conductor 814, inner left back contact of relay 602, left back contact of relay 601, conductor 804 to ground at the right back contact of relay 803. With relay 1029 energizedand relay 1027 normal, a circuit'for operating stepping on-the-line finder are served by brush 1032',

magnet 1030 may be traced from grounded battery, winding, armatureandback contact of the stepping magnet, outer front contact of relay 1029, conductor 1008, right ductor 12, outer right back contact of relay 1201,.- conductor 1206, intermediate back contacts of relays 1304 and 1305, next to the inner back contact of relay 1306, next to the inner front contact of relay 1307, conductor 1332, upper leftcontact of cam 906, 0011 ductor 907, inner right-back contact of re lay 1207, conductor 1218, upper contact'of 501, lower right contact of cam 806, I

outer right back contact of relay1216.

800 out of position 5 into position 6." This path is the same as that previously described for advancing this sequence switch from position 4, into position 5.

lVith sequence switch 900-in position 2, lamp 908 is lighted as an indication'that the first test is in progress A circuit for this lamp may be tracedfrom grounded battery, upper right contact of cam 914, lamp 908 to ground'at the contact of key 902. In addition .a circuit may grounded battery, upper left contact of cam 942, lamp 909 to ground at the contact of key 902. Lamp 909 is lighted as an indication that message rate type district circuits are being tested. It can obviously be seen that lamp 910 indicates that fiat rate type districts are being tested and lamp 911 for As sequence pe'cz'al tests of Zinc finder.

Spare Zine finder. In posit-ion 6 of sealso be traced from quence'switch 800, the line finder selector is 7 tested to determinewhether itis in a busy or an-idle condition. The terminalsof the line finder connector maybe open-, connected to aibusy line finder or'connected to an idle linefinder. If there are any spare terminals these terminals will-be connected'to condu'ctor 1048. a When there is a spare terminal on this arc, relay 1290 will be "operated in a circuit extending fromgrounded battery throughthe lower contact of cam. 820, contact of cam 822,.conductor 818,40 ground.

at=the'out-er right backcontact of relay 1216.

Thefenergization of relayv 1209 a circuit con tofc m wyceadsrtor 821,1 6 wind completesfrom grounded battery, lower left 

